I’d assume it’s a Federally levied property tax, the rebate applied to Federal income. Could be on the basis of the county assessed value of your property though.

You know how the state taxes your income and the feds tax your income? It would be like that but with property instead of income. Your county taxes your property and the feds tax your property. But balanced correctly, you shouldn’t be paying more taxes to the fed because they’ll cancel out with your income tax.